The present invention relates to a cooking grill. More particularly the invention relates to a cooking grill using structural foam plastic as one component of its construction. A ceramic gasket is used along with steel heat shields to protect portions of the polymer closest to the heat.
Outdoor cooking is a long established summer pastime in the United States, beginning with camp fires to outdoor fireplaces, and finally to portable outdoor grills. A wide variety of designs has been manufactured, from stone, brick, concrete, aluminum, stainless steel and other metals, and, in some limited cases from synthetic materials. Each of these materials have drawbacks as well as good features. Those materials such as concrete are too heavy. Aluminum and most metals are not always strong enough to resist flexing, so that collapsing or tipping over may happen when heavy plates of meats such as chicken, ribs or steaks are placed on one or more of the shelves provided. Any material used in manufacturing an outdoor grill must be resistant to heat
Schultz U.S. Pat. No. 3,581,731 discloses a portable cooking unit that uses an insulated chest to make carrying the unit easier or safer. The chest is formed from expanded plastic foam Hoglund U.S. Pat. No. 4,524,751 is another portable cooking device that has plastic material used in areas where bending stress or heat are minimized. Lindsey U.S. Pat. No. 5,154,158 combines a cooler and grill and the cover is stated to be made from or molded of plastic. It is clear that any plastic will function as well as any other material since it does not have to be load bearing and it is not near the burner.
Straubel et al. U.S. Pat. No. 6,024,082 is an outdoor cooking device in which the support housing is made from a non-metal material which is molded into a hollow thin walled structure. The non-metal material may be concrete or cement, sand and fibers. This patent describes a hollow support structure and other components made from glass fiber reinforced concrete. This is, of course, a heavy material that may, if improperly loaded, have an imbalance that may lead to safety concerns.
Yerkes U.S. Pat. No. 6,199,549 shows a larger device made from non-metal materials, in this case from aluminosilicate compositions.
It would be of great advantage in the art if an improved outdoor grill could be manufactured that would have complete heat resistance, compressive and bending strength to provide a safe grill for use in backyard environments.
It would be another great advance in the art if the grill would be low enough in cost and light enough in weight to allow almost all consumers to acquire it.
Other advantages will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, the present invention provides a portable grill having a source of fuel and at least one burner.
The grill is formed from a structural foam polymer base and pillar, such that the base and pillar both have a plurality of ribs for resisting torsion when weight is placed on the grill or if the grill is moved to a new location. It is intended that the base include wheels or rollers to facilitate movement
In a preferred embodiment, the pillar has a center portion defining the front of the grill and two side portions defining opposing side ends of the grill so that the back of the grill is open for connection to a fuel source such as a propane bottle and the like.
Both the base and the pillar are made from a structural foam polymer, such as foamed polypropylene. In any case, the polymer should have a flexural modulus of at least 150,000 psi and preferably over 200,000 psi. It should have a hardness of at least 80 on the Rockwell Hardness R scale. A preferred minimum Rockwell Hardness R value is at least 100.
Also forming part of the grill is a metal pillar collar mounted on the top end of the pillar, for holding the remaining parts. On top of the collar is placed a ceramic insulating gasket. The gasket is preferably formed from ceramic material capable of resisting a temperature of at least 1800xc2x0 F. during continuous use. Other heat resistant gaskets may also be used. The gasket functions to keep the temperature of the pillar below any temperature at which it would soften.
A metal heat shield having an upper lip in contact with the gasket is supported by the collar. The shield preferably has a tapered front, tapered sides and a flat bottom for reflection of heat in a direction toward the at least one burner and away from the lower portions of the complete grill.
The grill also includes a bottom shell, preferably made from cast aluminum although steel cast iron and other materials are suitable, that is supported on the collar and encloses the heat shield. Pivotally mounted on the bottom shell is a top shell having a handle to permit opening of the top shell. The preferred material for the top shell is also made from cast aluminum, though other metals are suitable as well.
For convenience of use, the grill should have at least one structural foam side table mounted on the bottom shell. The preferred side table uses the same structural foam as is used for the base and pillar.
The construction of the grill pillar provides substantial strength with only three sides of rigid structural foam polymer and one open side. This permits easy access to the fuel tank and allows the unit to be cleaned. For safety sake, a retaining wire is used to prevent the tank from falling out of the grill if it should be moved at an incline, such as up stairs.
The grill of this invention has been found to be capable of operating at full combustion capacity for at least eight hours a day for at least six consecutive days. The grill is stable and able to hold the weight of heavy objects, for example large platters of meat, without twisting or bending. The present invention meets all requirements of the AGA and CSA testing standards for barbeque safety.
Because of the positioning of a ceramic gasket and metal heat shield, not only is the grill safe, it is durable and can withstand many seasons of operation without deterioration.